Twenty-nine cases have been reported in Illinois.
The outbreak has not caused any confirmed deaths, but it may have played a part in the death of a cancer patient in Texas. The Food and Drug Administration is still trying to find the source of the tainted tomatoes.
Meanwhile, lawmakers are calling on the FDA to improve food tracking to prevent similar outbreaks.Illinois Dept. of Public Health spokeswoman Melaney Arnold says five people have been hospitalized, and adds the number of infections is expected to grow.
Last week, federal officials announced the salmonella outbreak was connected to three types of raw tomatoes: red plum, red Roma and round red. As a result, thousands of restaurants, groceries and food retailers have pulled tomatoes from their shelves and menu items.
The FDA says the salmonella causing the outbreak is a very unusual type called salmonella saintpaul.
Salmonella is a bacteria that lives in the intestinal tracts of humans and other animals. The bacteria are usually transmitted to humans by eating foods contaminated with animal feces.
The Associated Press contributed to this report.